Vaadin 7 Upload validation

Hi All,

I need to validate whether a user has selected a right item in a table tree and then upload the file.
The requirement is such that when a user hits upload then I need to check what Item in the tree table is selected if the item selected is not right I want to abort the upload and show a notification instead.

My problem is I tried to make sure that receiveUpload is not called. How can I do that.
Or would there be any other clean work around?

Please advise…

Thanks,
Divam